Clamshell lathes are utilized in industrial settings to machine or cut a portion of a generally cylindrical pipe or tube. These lathes may comprise first and second semicircular halves designed to be joined to surround the pipe to be cut or machined. The resulting annular assembly includes a stationary ring portion that becomes clamped to the pipe and an abutting rotatable portion including a gear ring attached to the stationary ring portion for rotation about the concentrically disclosed pipe.
A drive system including a motor is operatively coupled to the assembly and includes a drive gear designed to mesh with the gear ring operatively connected to the rotatable portion of the lathe. A tool slide can be mounted on the rotatable portion and is adapted to hold a tool bit for milling or cutting the pipe. The tool slide can include a feed mechanism including a tripper pin assembly that advances the tool slide and the tool bit preferably in a radial direction toward the pipe in incremental steps upon a predetermined revolution of the rotatable portion.
Because of the wide range of pipe sizes, the radial position of the tool slide and feed mechanism must be able to accommodate different sizes of pipe. Conventionally, this has been accomplished using a tripper pin assembly and a fixed position tripper sprocket on the tool slide. The tripper pin assembly is mounted on a tower radially protruding from the outer surface of the pipe lathe. When the operator radially repositions the tool slide to accommodate different sized pipes, the operator must also reposition the tripper pin assembly radially on the tower to correspond to the radial position of the tripper sprocket on the tool slide.
While these conventional tool slide and feed mechanisms can accommodate different sizes of pipe, they suffer from several drawbacks. For instance, they can expose the operator to dangerous pinch points between the tripper pin assembly and the tripper sprocket and/or other pinch points associated with the tool slide and feed mechanism as the tool module is rotating around the pipe lathe. A “pinch point” is a point that develops when two parts move together and at least one moves in rotary or circular motion. Such pinch points commonly cause disabling workplace injuries to fingers, hands, and/or arms of operators or other individuals. It is possible to have a hand, fingers, or an arm of an operator caught in the pipe lathe and injured.
Further, every the time the operator repositions the tool slide, the operator must also reposition the tripper pin assembly on the tower, which can be time consuming, inconvenient, and even dangerous if the pipe lathe is inadvertently energized during repositioning of the tripper pin assembly. In addition, the operator is commonly exposed to gear connections between the drive gear and gear ring typically located external to the body of the pipe lathe, creating an additional hazard for the operator that could cause disabling injuries.